Perhaps no technological development of the past 20 years has changed the nature of warfare as profoundly as the rise of the unmanned aerial vehicle.

UAVs can loiter over a target — unheard and unseen — for 24 or more hours, waiting for the precise moment to deliver a Hellfire missile or guided bomb onto an unsuspecting enemy.

General Atomics Aeronautical Systems stands at the center of this revolution. When Defense Secretary Robert Gates talks about the importance of UAVs to the fight in Iraq and Afghanistan, he is speaking first and foremost about General Atomics' MQ-1 Predator and MQ-9 Reaper.

Air Force Times got a rare opportunity to see Predators, Reapers and Army MQ-1C Sky Warriors take shape recently at the General Atomics production facility in a nondescript San Diego office park.

It takes 23 weeks to build a Predator, 32 to make a Reaper.

ROLLS OF FABRIC

Those airplanes enter the General Atomics factory — which covers nearly three acres — as unassuming rolls of black carbon-fiber or graphite fabrics impregnated with epoxy resin. The fabrics eventually become composites as strong as aluminum but substantially lighter.

Heat causes the resin in the fabric to cure and harden, explains Frank Belknap, the company's director of composite manufacturing, so the raw fabrics are stored at zero degrees Fahrenheit.

Down a hallway from the freezer, the fabrics are laid flat on an automated cutting machine adapted from the garment industry.

"We try to pull things out of different industries," Belknap says.

The machine's cutting arm moves across the surface of the fabric, using patterns stored in its computer to cut and label pieces of fabric to later be assembled into aircraft parts. The machine cuts about 35,000 parts per month.

Workers next place the precision-cut parts in layers that will become wing skins or structural members such as wing spars and landing gear. They start with a plastic or metal mold — costing $80,000 to $100,000 — that gives the fabric pieces the shape of the part they will become.

A laser system mounted to the room's high ceiling projects a pattern onto a wing mold, and workers lay the fabric pieces along the laser lines, building the wing skins up like plywood.

LIGHT BUT STRONG

Before the laser projection was available, building the wings could have taken a week. Now, it takes 12 hours.

The manufacturing process also uses spacers between piles of fabric to give the materials additional strength, such as a light cardboard-like material with a honeycomb pattern, which makes the composite stronger but not substantially heavier.

The fabric pieces are laid into the mold and cured in a 250-degree oven, which triggers a chemical reaction in the epoxy resin that permanently bonds the fabrics together and hardens them in the shape of the mold.

Next, the parts are trimmed to their exact specified shape, either by hand or with a robot. The robot is used mainly for parts that demand extreme precision, such as the hinges that attach flaps to wings.

The assembly floor is a large open space marked with signs announcing what aircraft and components are being assembled where: Predator B upper fuselage assembly, Predator lower fuselage assembly, and so on.

The space is nearly filled with fuselages and wings in different stages of assembly.

To assemble a fuselage, workers turn an upper fuselage skin upside down on a rack and lock in bulkheads. Then they attach the lower skin to complete the fuselage.

To build a wing, workers mount the composite wing spars into a wing skin and then secure the other skin.

After the components are assembled, they are moved next door to the paint shop, where they are sanded, primed and painted the Air Force's signature shade of gray. The painting process was adapted from the automotive industry.

From there, the painted components move to the integration floor, the final step in the production process. There, the wings are secured to the fuselages, engines are installed in their housings and electronics and avionics are added.